separation of the services layer in the internal skin of insulation, helping to deliver an airtightness of 0.5ach@50Pa. There was no product on the market
Special features
Ground-to-air heat exchanger below existing basement fl oor Integrated solar thermal system for hot water, backed up by air-source heat pump Exhaust-air heat pump inside ventilation system for all space heating Green roof Specially designed triple-glazed sash imitation windows for conservation area
Thermal bridges cut off by extensive detailing and rehanging of fl oors
at the time permissable to conservation authorities that could have provided highly effi cient, airtight window replacements. Accordingly, the design team and lead contractor developed a bid proposal and were awarded grant funding by the Technology Strategy Board to develop triple-glazed, highly effi cient, sealed, sash-type windows that are almost indistinguishable from the original windows in the neighbouring houses. Sixty per cent of hot water requirements are provided by solar thermal panels, and a 1.2 kWp solar PV system was installed. A green roof improved biodiversity and insulation, and rainwater capture helped to reduce runoff and to replace potable water for irrigation. The house was fi tted with a full ventilation system with heat recovery, designed to be used in conjunction with natural ventilation in summer. All space heating and hot water top-up are
provided by an exhaust-air heat pump. A ground-to-air heat exchange concept was developed and installed above the slab of the basement, providing signifi cant heating gains in winter and free cooling in summer. This unique design opens up the potential for the urban use of these heat exchangers, previously limited to detached buildings with signifi cant surrounding space.
Period
Jan 2007 – Jan 2008 Sept 2011 – Sept 2012
Gas consumption (kWh) Electricity consumption (kWh) Total energy consumption (kWh) 43,094
468
6,172 4,544
49,266 5,012
The results Based on the fi nal as-built condition, the house was awarded Passivhaus certifi cation. Initial results show a measured 89.8% reduction in full-year energy consumption, as compared to metered consumption over a full year prior to the retrofi t. Occupant comfort levels are consistently reported as very high, describing the house as a ‘fabulous living environment… exceptionally comfortable’. There has been a commitment to learning from the project and sharing results. The project has been shown on TV and widely published in newspapers, as well as an academic paper at the CIBSE Technical Symposium. The learning from this project has been applied at different levels on more than 50 projects by the greentomatoenergy team, and has benefi ted designers who have been infl uenced by these principles in other projects.
24 CIBSE Journal March 2013
www.cibsejournal.com
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